It is already known to detect a side impact resulting in a deformation of a side section of the vehicle. Indirect measuring methods, e.g. via an adiabatic pressure rise in a side section of the vehicle, or direct measuring methods, e.g. via a foil strain gauge, are available. A method that functions independently of the side section deformation is side impact detection using an acceleration sensor.
The device of the present invention for side impact detection for a motor vehicle has the advantage that only real deformations of the side section are detected by the at least one distance sensor, the intrusion speed into the vehicle then also being determinable. As a result, it is possible to control multi-step or even continuous restraining systems in accordance with the situation, since determining the intrusion speed also renders it possible to estimate possible occupant injuries. Moreover, the device of the present invention has a higher degree of robustness with respect to harsh driving maneuvers, since only real deformations of the side section are detected. Finally, distance sensors are also less expensive, thereby resulting in a reduction in costs.
It is particularly advantageous that the distance sensors are designed as optical sensors, infrared light being used in particular. This results in a particularly robust measuring principle, since interference from outside light is eliminated. In the case of such optical distance sensors, light diodes or laser diodes may preferably be used as transmitters, and photodiodes but also bolometers are conceivable as receivers. Ultrasound and microwaves are alternative measuring principles. At the start of operation of the device of the present invention, an initial measuring procedure is advantageously performed in order to optimally adjust the transmitting power, a suitable control circuit adjusting the operating point during operation. Optimal operation of the device of the present invention is, thus, always ensured.
It is also advantageous that either the surface of the stiffening pipe itself is used as the reflector, or, when constructive conditions of the side section require it, the stiffening pipe is connected to a metal plate that then acts as the reflector and is preferably designed as a sheet-metal part. Such constructive situations can be caused by a side window in particular.
Finally, it is also advantageous that a plausibility sensor is present that is used for checking for a side impact, so that false signals from the distance sensors do not trigger restraining means. This plausibility sensor is typically designed as an acceleration sensor. In this instance, other sensor types, such as pressure and temperature, may also be used.